Since 2000, the Pew says, "the middle class has shrunk in size, fallen backward in income and wealth, and shed some—but by no means all—of its characteristic faith in the future." Pew cites statistics showing that middle class earnings and net worth have plummeted since the mid-2000s and that about 85% of the middle class say it is harder to maintain their standard of living than it was 10 years ago.

The reason the decline of the middle class is important is not just about fairness. It's about the health of the economy as a whole.

Collectively, the middle class represents enormous buying and spending power, and in the past 60 years this spending power has helped the U.S. economy become the envy of the world.

But now, however, the middle class is increasingly strapped. And the resulting impact on spending is constraining the growth of companies that sell products and services to American consumers.

The causes of this middle-class decline are many, from globalization (jobs being shipped overseas), to the decline of private-sector unions, to the wholesale embrace of a "shareholder value" religion that values profit over everything else that companies produce. But the result of the trend can be seen vividly in two charts.

To truly "fix" the U.S. economy, corporations are going to have to be persuaded to invest more of their excess profits in their employees, both by hiring new employees and paying existing employees more. "Wages" to employees become spending money for those employees, and the spending produces revenue for other companies. If corporations can collectively be persuaded to reinvest more of their profits in their people, in other words, they will help restore their own revenue growth.

Henry Ford famously decided to pay his workers more than he had to to keep them. One result of this was that the workers made enough money to be able to buy Ford's cars, and this made Ford more successful. Another result, which is considered irrelevant in some business circles, is that Ford employees were able to live middle-class lives. This helped not only Ford, but the country.

Our current economic problem is not likely to be solved by the government, which possesses neither the power nor the competence to make it happen. The problem will have to be solved by the private sector. And one important part of that solution is for corporations to share more of their wealth with one very important (and often overlooked) corporate constituency: Their employees.